An undercover police officer was shot in the arm Monday night in East Oakland, and an intense search led police to detain one of three assailants, police said.

The officer was sitting in a vehicle when a confrontation occurred between the officer and three young men on the 1700 block of Seminary Avenue at 6:22 p.m., said Officer Johnna Watson, an Oakland police spokeswoman.

The officer, whose name wasn't released, suffered a gunshot wound to the arm that was not considered life-threatening, Watson said. He was in the area conducting a stakeout regarding a shooting that happened Sunday on the 5900 block of Foothill Boulevard, Watson said. That victim, a male, remains in life-threatening condition.

The shooter dropped his weapon and fled with the other two men, at least one of whom was armed with a handgun with an extended magazine, authorities said.

A responding officer called for help on the radio after being flagged down.

Police searched the neighborhood for several hours with the help of the SWAT team and a California Highway Patrol helicopter and said they detained one of the three assailants. The search for the two others continued late Monday night.